In coronary artery disease, the build-up of artheroscierotic plaque on the inner walls of the coronary arteries causes a narrowing or complete closure of these arteries, resulting in insufficient blood flow to the heart. This condition has become one of the most common life-threatening medical problems facing older men and women.
A number of approaches have been developed for treating coronary artery disease. In less severe cases, it is often sufficient to treat the symptoms with pharmaceuticals and lifestyle modification to lessen the underlying causes of the disease. In more severe cases, a coronary artery blockage can often be treated using endovascular techniques such as balloon angioplasty, atherectomy, laser or hot tip ablation, placement of stents, and the like.
In cases where pharmaceutical treatment and/or endovascular approaches have failed or are likely to fail, it is often necessary to perform a coronary artery bypass graft procedure using open surgical methods. Such methods require that the patient's sternum be divided longitudinally and the chest be spread apart to provide access to the heart, known as a median sternotomy. The patient's heart is placed under cardioplegic arrest and the patient is supported by cardiopulmonary bypass. A source of arterial blood is then connected to the diseased coronary artery downstream from the blockage. The arterial blood source may be a venous or arterial graft vessel connected between an arterial blood vessel such as the aorta and the coronary artery. Another common arterial blood source is either the left or right internal mammary artery which may be grafted to the coronary artery which is narrowed or occluded. Recent studies have suggested that the use of the mammary arteries as an arterial blood source may be advantageous over other sources due to a greater likelihood that the graft will remain patent over time.
To form an anastomosis between an internal mammary artery and a coronary artery, blood flow through the internal mammary artery must be temporarily stopped, typically by applying a removable clamp to the mammary artery. The mammary artery is then severed downstream from the clamp to create a free end. An incision is created in the target coronary artery downstream of the blockage. The free end of the mammary artery can then be connected to the incision in the coronary artery, typically by suturing, such that blood can flow from the mammary artery through the incision into the coronary artery.
To facilitate the surgeon's view of the procedure, the heart must be positioned to expose the anastomosis site, and the anastomosis site must be cleared of fluids, tissue and debris which may obscure the site. In addition, the coronary artery or mammary artery may contain blood and other fluids near the location of the incision, which should be prevented from flowing out of the coronary artery or mammary artery during the suturing procedure. The coronary and mammary arteries must also be stabilized and held in a stationary position so that the surgeon can perform the delicate task of sewing the free end of the mammary artery to the coronary artery.
Using conventional open-chest methods, the anastomosis procedure is typically performed directly through the large opening in the patient's chest provided by a median sternotomy. This opening enables the surgeon to see the coronary and mammary arteries directly and to position his or her hands within the chest cavity in close proximity to these arteries for manipulation of surgical instruments. The surgeon can thus utilize various instruments to reposition the heart, clear away fluid and debris and stabilize the anastomosis site during the procedure. For example, clamps may be applied to the mammary and coronary vessels to stop blood from leaking from these vessels. If tissue or fluids migrate into the anastomosis site, the surgeon can utilize an irrigation tube to wash these obstructions away from the site. The heart may be repositioned using retraction devices or simply by hand. To stabilize the mammary artery during the anastomosis, a pair of forceps can be used to grasp the mammary artery and maintain its position while it is sewn to the coronary artery. All of these tasks are accomplished without great difficulty due to the open exposure of the surgical site through the large opening provided by a median sternotomy.
While open-chest coronary artery bypass grafting is very effective in many cases, the gross thoracotomies used in conventional open heart surgery to perform coronary artery bypass grafting are highly traumatic to the patient. Therefore, new methods of performing surgery on the heart using minimally invasive thoracoscopic techniques have been recently developed. In these methods, the patient's heart is arrested by occluding the patient's aorta between the coronary arteries and the brachiocephalic artery with an expandable balloon on the distal end of an endovascular catheter introduced via a femoral artery. Cardioplegic fluid is then delivered to the patient's myocardium through a lumen in the same catheter or through a separate catheter positioned in the coronary sinus. This method allows the surgeon to perform operations such as coronary artery bypass grafting without creating a large opening in the patient's sternum. Minimally-invasive cutting and suturing instruments can be introduced thoracoscopically to connect the free end of the severed mammary artery to the coronary artery. Complete descriptions of such methods are found in commonly assigned, co-pending application Ser. No. 08/023,778, filed Feb. 22, 1993, now U.S. Pat. No. 5,452,733, and application Ser. No. 08/194,946, filed Feb. 11, 1994, now U.S. Pat. No. 5,501,698, which are incorporated herein by reference.
The new generation of thoracoscopic methods of performing coronary artery bypass grafting has, of course, created many new challenges. Such challenges include keeping the anastomosis site free of fluid and debris, positioning the heart within view of the surgeon(s), and stabilizing the coronary and mammary arteries to facilitate the anastomosis. These functions must be performed through small percutaneous incisions or cannulae positioned in intercostal spaces in the patient's rib cage. Known devices are not capable of performing these tasks through small percutaneous penetrations and, therefore, are unsuitable for closed chest procedures.
For this reason, improved systems and methods are desired for isolating a surgical site, such as an opening in a fluid-carrying vessel, in a body cavity via a small percutaneous incision or cannula. Preferably, the system and method would be capable of isolating a site of an anastomosis between a coronary artery and a mammary artery during a coronary artery bypass grafting procedure. The system and method should allow the surgeon to apply pressure against a vessel on both sides of an opening or incision in the vessel to inhibit blood and other fluids from passing through the incision. The system and method should also allow the surgeon to stabilize the mammary artery to facilitate suturing the free end of the mammary artery to the coronary artery. The system and method should further allow the delivery of irrigation fluids to the surgical site to wash away fluid and debris. In addition, it would be desirable if the above functions were performed by a single instrument introduced through a cannula or small percutaneous incision to limit the number of incisions required to perform the procedure.